db2 => select name,salary+comm from staff fetch first 3 rows only
NAME 2
--------- ----------
Sanders -
Pernal 78783.70
Marenghi -
3 record(s) selected.
db2 => insert into tt values(1),(1)
DB20000I The SQL command completed successfully.
db2 => create table pers like staff
DB20000I The SQL command completed successfully.
db2 => update staff set (dept,salary)=(51,70000) where id=150
DB20000I The SQL command completed successfully.
Oraclehedb2都支持下列写法
update tttt set id=3,name='c' where id=1;
db2 => select salary from old table(update staff set salary=salary*0.2 where id=10)
SALARY
---------
19671.50
1 record(s) selected.
db2 => select salary from old table(update staff set salary=salary*0.2 where id=10)
SALARY
---------
3934.30
1 record(s) selected.
会话1
$ db2 +c
db2 => connect to sample
Database Connection Information
Database server = DB2/LINUX 9.7.5
SQL authorization ID = DB2INST1
Local database alias = SAMPLE
db2 => create table czm_1(id int)
DB20000I The SQL command completed successfully.
db2 => insert into czm_1 values(1)
DB20000I The SQL command completed successfully.
db2 => savepoint savepoint1 on rollback retain cursors
DB20000I The SQL command completed successfully.
db2 => insert into czm_1 values(2)
DB20000I The SQL command completed successfully.
db2 => savepoint savepoint2 on rollback retain cursors
DB20000I The SQL command completed successfully.
db2 => select * from czm_1
ID
-----------
1
2
2 record(s) selected.
会话2,执行下面语句无法查询czm_1，hang住不能继续执行
db2 => connect to sample
Database Connection Information
Database server = DB2/LINUX 9.7.5
SQL authorization ID = DB2INST1
Local database alias = SAMPLE
db2 => select * From czm_1
会话1
db2 => rollback to savepoint savepoint1
DB20000I The SQL command completed successfully.
db2 => select * from czm_1
ID
-----------
1
1 record(s) selected.
db2 => rollback
DB20000I The SQL command completed successfully.
db2 => select * from czm_1
SQL0204N "DB2INST1.CZM_1" is an undefined name. SQLSTATE=42704
可以看到会话1在执行完rollback语句后，找不到czm_1这个对象了，
会话2 hang住的select语句也执行完毕
db2 => select * from czm_1
SQL0204N "DB2INST1.CZM_1" is an undefined name. SQLSTATE=42704
db2 -td@ -vf createSQLproc.db2
db2 命令指定 -td 选项标志，这让命令行处理程序使用 @ 作为语句终止字符（因为在过程体内已经使用分号作为语句终止字符）；-v 选项标志让命令行处理程序将命令文本回显到标准输出；-f 选项标志让命令行处理程序从指定的文件（而不是标准输入）读取命令输入。
db2 => create table books(bookid integer,bookname varchar(100),isbn char(10)) in userspace1
db2 => alter table books alter bookname set data type char(150) alter isbn set not sqlserver
iis7站长之家
DB20000I The SQL command completed successfully.
修改表列的限制：
在修改字符串列的长度时，只能增加长度。
在修改列的数据类型时，新的数据类型必须与现有的数据类型兼容。例如，可以将 CHAR 列转换为 VARCHAR 列，但是不能将它们转换为 GRAPHIC 或数字列。数字列可以转换为任何其他数字数据类型，只要新数据类型的长度足以容纳其中的值。例如，可以将 INTEGER 列转换为 BIGINT，但是 DECIMAL(10,2) 列不能转换为 SMALLINT。
固定长度的字符串可以转换为可变长度的字符串，可变长度的字符串也可以转换为固定长度的字符串。例如，CHAR(100) 可以转换为 VARCHAR(150)。对于可变长度的图形字符串也有类似的限制。
表的某些特征不可以更改。例如，不可以修改某些列的数据类型、表驻留的表空间或列的次序。要更改这样的特征，必须保存表数据，删除表，然后重新创建表。